Though she isn't a car mogul in the traditional sense – she's not a man for a start, doesn't own the company and hasn't put her name on the grille – the buck at America's biggest car company now stops with Mary Barra.

Few women have run automotive manufacturers. The slightly legendary "iron lady of cars", Vivian Yen, at Yulon Motor in Taiwan, is the only one that comes readily to this mind. Yulon isn't exactly on the scale of GM.

The American giant didn't have a single woman (or a married one) on its board until 1972, and it remained Bloke City well after that.

So who's the women crashing through the glass sunroof? She's a 53-year-old self-proclaimed car buff who is well versed technically and financially, with a degree in electrical engineering and an MBA.

Born Mary Makela to parents of Finnish descent, she's US-born and GM through-and-through. Her father, whom she credits with passing on a love of cars, spent his career as a die maker for Pontiac.

Barra joined GM at 18 while studying. Her first car was a Chevrolet Chevette, her second a Pontiac Fiero yet, almost inexplicably, she survived.

Twenty eight years after joining GM, she became a vice president, rising in quick steps to head global product development with the specific brief of reducing the number of platforms across the GM world.

With each promotion she broke her own record for being history's highest placed female automotive executive. By 2011 she was one tier below the top and, in January 2014, finally took over the biggest office and, presumably, the flashest executive restroom.

However, conspiracy theorists suggested she'd been set up to fail. Two weeks after Barra became CEO, news escaped that GM had failed for 10 years or more to recall cars with ignitions it knew to be faulty. These could turn off the engine at speed, and prevent the airbags from deploying.

There had been 13 deaths, according to GM, more than 150 according to others. Barra was left to tell the media she knew nothing about it; some believe her predecessor Daniel Akerson​ certainly must have when he took a pay-out and scampered (he has repeatedly denied it).

Either way, Barra's difficult first year included recalling 30 million cars and some very uncomfortable times in front of US Senators. Yet she managed the crisis extremely well, as a recent Forbes headline attests: "What Volkswagen's next CEO can learn from GM's Mary Barra".

A long and varied career has given Barra extensive knowledge of almost every aspect of the car business. She has built a reputation as a straight talker and a good listener, the second not an attribute belonging to many of her predecessors.

A fellow executive put a caveat on her consensus approach. When it's not working, "she's pretty decisive".